The present invention relates to processes for cold mechanical working of metallic materials.
More particularly, the present invention relates to applying and drying lubricants which is liquid at room temperature, on the metallic material to be mechanically worked, especially of lubricants which include an organic solvent and solid or semi-solid lubricant substance accommodated therein. The metallic material may be in form of, for example, wires, rods and tubes, which are coated by a lubricant for hydrodynamic lubrication during drawing processes.
For applying liquid lubricating substances onto metallic materials to be mechanically worked by drawing it is known to pass the metallic material through an open box containing the lubricating substance. The striping off element is arranged in the inlet and the outlet, the striping off element formed by a felt or synthetic plate with a slot through which the metallic material passes. These striping off elements fill the box and at the same time guarantee the formation of a lubricant film. Such arrangement possesses the following disadvantage. The solvent contained in the lubricant can evaporate whereby a depletion of the solvent takes place, and in the case of special solvents additional health protection measures must be taken. It is also disadvantageous that the arrangement can function only in horizontal position. Moreover, a continuously uniform application of the lubricant is not guaranteed inasmuch as the stripping off elements tend to wear very fast. In the case of the wear, great quantities of lubricant exit from the box. Since the outer face of the metallic material in this case has impurities, for example fat rests, this arrangement cannot provide for closed lubricant film.
When lubricant is liquid and formed by a solution or dispersion of solid or semi-solid lubricating substance, the liquid lubricant layer applied on the metallic material must be dried before the tool for mechanical working in order to utilize the advantages of the solid or semi-solid lubricant. This means that the liquid contained in the lubricant must be removed before the insertion of the metallic material into the working tool. The removal must be performed very thoroughly, because the dynamic viscosity of the lubricant decreases in the case of insufficient drying. It is known to remove the liquid by drying the metallic material in drying oven. This method is time consuming especially for lubricants which contain a liquid with high boiling point. This is even more disadvantageous in the case of continuous coating with subsequent mechanical working as well as in the case of continuous multistage mechanical working with intermediate coating, since in these cses only low working speeds can be attained. Moreover, the energy expenses and technological expenses for drying by heated air are relatively high. In the case of the lubricant layers containing the organic solvents, this method cannot be utilized inasmuch as the requirements to the protection of workers' health and fire protection are not completely satisfied.